“Aortic aneurysm” is the term used to describe a vascular abnormality condition where a segment of the aorta is dilated to a diameter greater than its original diameter. Aneurysms can occur in virtually any region of the vasculature including the aorta in the abdominal and thoracic regions. Aortic aneurysms are caused by hardening of the arteries (atherosclerosis), high blood pressure (hypertension), genetic disposition such as Marfan's Syndrome, trauma, or less common disorders. Atherosclerosis is the most common cause.
Where dilation of the aorta meets or exceeds 50% of the original aortic diameter, i.e., where the diameter of the aorta is 150% of the original or expected diameter, intervention generally is deemed necessary. Without intervention, the aneurysm may continue to expand, leading to the possibility of tearing or rupture of the aorta, and death. Intervention includes techniques such as open repair which involves replacement of the aorta with a synthetic lumen which is sewn to the two ends of the still viable aorta after the aneurysmal portion has been opened or surgically removed, or, less invasively, by the endovascular placement of an exclusion device such as a stent graft across the aneurysmal site. The stent graft is a tubular member designed to provide a conduit enabling blood flow through the aorta without allowing the systemic pressure of the blood to further stretch the aneurysm. For this intervention to be successful, the stent graft must extend across the weakened blood vessel wall so that the opposed ends engage and seal against healthy blood vessel tissue on either side of the aneurysm.
A stent graft includes a stent framework, which provides structural support of the stent graft in a tubular configuration once deployed at a vascular location, and a graft portion, comprising an excluding material, which is sewn or otherwise attached to the stent frame and which provides a relatively fluid-tight conduit for blood flow through the stent graft and past the aneurysm site. Placement of a stent graft can be performed without a chest incision, by using specialized catheters that are introduced through arteries usually at a location in a leg adjacent to the groin.
The aorta has numerous arterial branches. For example, the abdominal aorta includes the superior mesentery artery, the celiac trunk and the renal arteries. The proximity of an aneurysm to a branch artery may limit the use of an excluding device such as a tubular stent graft, as the main body or ends of the tubular stent graft may occlude or block the branch arteries due to the need to position the stent graft to seal against a healthy, i.e., non diseased or dilated, portion of the artery wall. There may be an inadequate length of healthy tissue for the stent graft to seal against in the area between the aneurysmal region of the aorta and the location of the branch arteries or even if the stent graft initially is located without blocking a branch artery, there still is a risk of migration of the exclusion device to a position where it may partially or fully block a branch artery. Additionally, where multiple branch arteries are present adjacent to the aneurysm, the ability to position a stent graft so as not to occlude any of the branch arteries may be problematic. Furthermore, where a stent graft needs to be located in an aorta and span a branch artery, the stent graft must be specifically configured to the particular patient's anatomy, i.e., apertures to enable blood flow into the branch arteries must be provided at specific locations in the tubular wall which align, when the stent graft is deployed, with the branch artery locations. Therefore, there is a desire in the art to achieve a greater success of aneurysm repair and healing, and in particular, mechanisms and methods to enable stent grafting or the placement of other exclusion devices adjacent to branch vessels in aneurysmal locations with minimal need to customize the stent graft for a specific patient, but still enable placement of the stent graft across a branch artery while providing a sealed path for blood flow into the branch artery.